This proposal requests support for a MoFlo XDP Cell Sorter equipped with 3 lasers. This new instrument will be used to purify and sort rare cell populations based on their expression of unique cell surface markers using jet-in-air technology. Our request for the MoFlo XDP Cell Sorter is based on the following: (i) Our current Flow Cytometer Core is running above optimal capacity which is negatively impacting the tempo of our research;(ii) Several major users of the flow core require a jet- in-air sorter to make significant progress on their research and (iii) Our preliminary data demonstrate that the jet-in-air MoFlo Cell Sorter will meet both of these research needs. The instrument will support and enhance existing NIH-funded projects and will foster avenues of research that will likely lead to future funded projects. We will outline 8 NIH-funded investigators and their specific research projects that will be enhanced by the acquisition of the MoFlo XDP Cell Sorter. All of these investigators currently use the Cincinnati Children's Hospital Medical Center (CCHMC) Research Flow Cytometry Core (RFCC). Their research interests span a broad spectrum of biologic queries requiring the use of cell sorting, including: (1) mechanisms underlying the pathogenesis of asthma;(2) pathogenesis of biliary atresia;(3) the role of regulatory T cells in HIV and aging;(4) the role of cancer stem cells in chronic myelogenous leukemia;(5) mechanisms by which novel dendritic cell populations promote anti-tumor immunity;(6) mechanisms by which T cell effector function regulate hemophagocytic lymphohistiocytosis (HLH);(7) the role of GTPases in hematopoietic stem cell maintenance and development of hematopoietic diseases (leukemia, lymphoma);(8) dissecting the intercellular interplay that governs development of type I diabetes. Moreover, we list more than 20 additional investigators and describe how their NIH-funded research projects will benefit from this instrument acquisition. The PI, Dr. Wills-Karp, who is a leader in the field of immunology and a user of flow cytometry for over 20 years, will be responsible for the managerial oversight of the MoFlo XDP. She will work with the Director of the Research Flow Cytometry Core, Dr. Sherry Thornton, Ph.D. and the members of the Oversight Committee to establish scheduling priorities and cost- recovery rates. The MoFlo XDP sorter will be housed in the newly renovated CCHMC-RFCC. The Core Director will oversee the daily operation and maintenance of the Cell Sorter with the assistance of a highly qualified Core Manager and 3 technicians. CCHMC is highly committed to supporting its research cores and will support the long-term upkeep and maintenance of this instrument to ensure quality services are provided in a timely manner.